i) Field of the Invention
This invention relates to a process for producing a polyarylene sulfide, more especially an non-ionic process for producing a polyarylene sulfide from a cyclic thioether; and to a novel polyarylene sulfide and composites containing the polyarylene sulfide, the invention also relates to novel cyclic oligomers which are intermediates for manufacture of polyarylene sulfides.
ii) Description of Prior Art
Aryl thioether polymers such as polyphenylene sulfide (PPS) are known for their thermal stability and chemical resistance and as such are of value in the manufacture of molded products employed in applications where thermal stability and chemical resistance are important.
U.S. Pat. No. 5,384,391 describes prior processes for producing polyarylene sulfides involving a condensation polymerization involving a nucleophilic reaction between a dihalo-aromatic compound and an alkali metal compound in an organic amide solvent. This process is an ionic process.
U.S. Pat. No. 5,384,391 describes the problems associated with this prior process and proposes a process in which a cyclic arylene sulfide oligomer is heated in the presence of a ring-opening polymerization catalyst which is cationic or anionic in nature.
Prior processes for producing polyarylene sulfides result in polymers containing inorganic contaminants derived from the inorganic polymerization catalysts. These contaminants deleteriously affect the properties of the polyarylene sulfide, for example, the electrical characteristics. Furthermore, the polyarylene sulfides are frequently molded to form articles and the molded polymer is reinforced with inorganic fibers, for example, glass fibers. The high melt viscosities of the linear high molecular weight polymers make it difficult to fabricate fiber filled composites with high loadings of the fiber.
The use of cyclic oligomer precursors which can be polymerized in situ by the addition of a ring opening initiator would allow formation of composite structures with high fiber loadings because of their low melt viscosity.
It would also be advantageous to produce polyarylene sulfides free of inorganic contaminants resulting from anionic or cationic initiators or catalysts.